Cats' eyes including self-illuminating LED flashers are known for mounting on the boundaries between adjacent traffic lanes or on sidewalks so as to reflect a vehicle's headlamps and thereby indicate to a driver the lane boundary.
Also known are cats' eyes including an electrical flasher circuit operable from a small rechargeable battery which is charged via a solar panel fixed to a housing of the cat's eye, so as to recharge the battery during daylight hours. The LED flashers improve the visibility of the cat's eye, thereby increasing road safety.
A primary requirement of cats' eyes of the kind described having integral LED flasher circuits therein is their compatibility with existing, conventional cats' eyes which do not include the enhancement of flashing LEDs. Conventional cats' eyes are designed to be mounted in the road surface so as to protrude therefrom only a minimal distance, their protruding edges being rounded so that, in the event of a motor vehicle mounting the cat's eye, no damage will be done to the tires of the vehicle or to the cat's eye itself. Typically, such cats' eyes have an overall depth not exceeding 18 mm.
Existing cats' eyes including LED flasher circuits have not been able to conform to this standard height and have therefore included a deeper housing adapted to be sunk into the road surface. For example, the Japanese company Kyocera manufacture a curb flasher under the name Accless having an outer casing whose height above ground is 28 mm but which has an extended casing for sinking below the ground surface having a depth of 133 mm. A pair of solar panels are mounted on an upper surface of the housing and are coupled to a circuit enclosed within the lower housing and including a pair of rechargeable batteries which are recharged by the solar panel during daylight and provide electrical power to the flasher circuit at night.
Clearly, such a cat's eye cannot easily replace existing, conventional cats' eyes on account of the effort required to sink the housing into the road surface which, particularly on long stretches of road, is a major undertaking.
Likewise, a flashing light for mounting on a curb is manufactured under the trade mark Swareflex including therein an LED solar-powered flasher and a storage battery for storing electrical energy transformed by a solar cell. The storage battery has a capacity of 14 days power consumption when fully charged. In order to become fully charged, fine weather (corresponding to intense ambient illumination) is required for a minimum of four days.
It would obviously be preferable to provide an LED flasher circuit within a standard cat's eye housing so as to provide the additional safety resulting from their improved visibility whilst nevertheless not requiring any major roadworks for their installation.
It is envisaged that such a miniaturized flasher circuit would also find application in memorial symbols such as are commonly fixed to gravestones, and the like. In this connection, U.S. Pat. No. 5,013,972 (Malkieli et al.) discloses a symbolic/religious memorial light having a flickering-candle appearance and operated either by a solar cell unit or by a rechargeable battery charged thereby.
The flasher circuit disclosed by Malkieli et al. is based on a conventional astable multivibrator, whilst the solar cell has a nominal current rating of only 18 mA. The rechargeable battery includes a couple of conventional nickel-cadmium cells, each having a nominal voltage of 1.25 V. In such an arrangement, the solar cell would not be able both to energize the flasher circuit and also maintain the rechargeable cells fully charged for extended periods of time in the absence of intense ambient light conditions.